The economic advantages of optical communications derive primarily from the information carrying capacity of optical fiber. These economies can be more fully realized if information processing, as well as transmission, is performed with the optical signal. However, to date, little, if any, of the information processing is performed with the optical signal. Instead, the optical signal is transformed to an electrical signal, the information processing is performed with the electrical signal, and the processed electrical signal is then transformed back to an optical signal for transmission. Even the standard regeneration function, which must be performed many times during the course of any long distance transmission, is done by first transforming the optical signal to an electrical signal. Consequently, in any long distance optical communication system, the optical signal is transformed into an electrical signal numerous times during the course of transmission. This invention, for the first time, allows for the fabrication of an all-optical regenerator--a device which can detect an incoming optical signal, and emit an amplified and retimed version of that optical signal, without transforming the optical signal into only an electrical signal.
The search for an all-optical regenerator has been ongoing for many years. However, a critical problem, central to the design of any all-optical regenerator, has remained unsolved--the problem of optical timing, i.e., the recovery of an optical clock signal from an input optical signal, without transforming the optical signal into an electrical signal. As noted in a recent review (M. J. O'Mahoney, "Toward an All-Optical Regenerator", ECOC '87, Vol II, page 11, Helsinki, Finland), design suggestions have only been addressed to the untimed regenerator, since "it avoids the need for optical retiming, which is as yet an unsolved problem".